OO-5607: fix full screen mode for Youtube video in single page too

src/main/webapp/static/themes/light/modules/_helpers.scss

@@ -347,6 +347,11 @@
 	max-width: 100%;
 }
 
+.mejs__fullscreen .mejs__mediaelement iframe[id$='youtube_iframe'] {
+	width: 100% !important;
+	height: 100% !important;
+}
+
 /* figures with captions */
 .o_figure_caption_bottom {
 	display: inline-block;	

src/main/webapp/static/themes/light/modules/_video.scss

@@ -211,11 +211,6 @@
 	}
 }
 
-.mejs__fullscreen .mejs__mediaelement iframe[id$='youtube_iframe'] {
-	width: 100% !important;
-	height: 100% !important;
-}
-
 .mejs__time-rail {
 	.o_video_marker_gray { 
 		background: $gray-dark;